The Bedrock Elite i10 is the only acoustic analyzer in the world capable of performing a complete Full Speech Transmission Index (Full STI) measurement — fully compliant with IEC 60268-16 — in under 60 seconds. This technical breakthrough changes the economics and practicality of Full STI measurement in the field, making comprehensive speech intelligibility testing practical for every measurement position in a building for the first time.
Full STI has always been the gold standard for speech intelligibility measurement. While STIPA (a 14-frequency approximation of Full STI) is widely used in field testing because of its speed, Full STI's 98-frequency measurement approach is more accurate — particularly in electroacoustic systems with non-linear distortion, clipping, background noise masking, and complex acoustic interactions. For life-safety critical voice alarm systems, Full STI provides the most defensible and accurate intelligibility measurement available.
Traditional Full STI measurement requires 98 modulation frequencies across 7 octave bands, with each modulation frequency requiring a separate measurement interval. Using traditional measurement equipment, a complete Full STI measurement takes 10–15 minutes per measurement position. In a large building with 20, 50, or 100 measurement positions, this makes Full STI completely impractical as a field commissioning tool — a 50-position Full STI assessment would take two to three working days with traditional equipment, compared to 2–3 hours for the same work with the i10.
As a result of this time constraint, Full STI has historically been used only for research, design validation, and occasional compliance disputes — not for routine commissioning. Instead, commissioning engineers use STIPA as a practical approximation. The i10 changes this: with under-60-second Full STI, every measurement position in a building can receive a Full STI measurement within a normal working day, without any compromise in measurement accuracy.
Full STI and STIPA typically agree closely for well-behaved linear systems with low distortion. The key accuracy advantage of Full STI over STIPA arises in systems with non-linear distortion, clipping, or harmonic distortion — conditions where STIPA can over-estimate intelligibility because its 14 modulation frequencies do not fully capture the distortion characteristics of the system. In voice alarm systems where amplifiers may be driven hard, where ageing equipment introduces non-linearity, or where system faults create distortion, Full STI provides a more reliable assessment of actual speech intelligibility than STIPA.
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